Problem: With AbuseFilters, there are several ways to target long-term abusers and harassers, including IP adresses, but we lack one which could be powerful: user agent (UA).
Proposed solution: Add a user-agent variable to AbuseFilter. This would require first that CheckUser-level abuse filters to be created.
Who would benefit: Everyone, especially victims of harassment; sysops, patrollers and anyone that fights long-term abuse (with harassment or not); checkusers who are abusefilters editors.
More comments: The only downside that I see is that it would require some CheckUsers to be familiar with Abusefilters and regexes.
